EP1832142A1

EP1832142A1 - Notification of channel descriptor transmission for a mobile station in idle or sleep mode in a wireless access system

Info

Publication number: EP1832142A1
Application number: EP05823591A
Authority: EP
Inventors: Beom Joon Kim; Yong Won Kwak; Yong Ho 1503-1304 Hanireum-Hyun Dai APT. KIM; Ki Seon Ryu
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2004-12-27
Filing date: 2005-12-27
Publication date: 2007-09-12
Also published as: CN101077032B; US20060203766A1; JP2008526092A; US7751356B2; JP4959580B2; EP1832142A4; KR20060074283A; CN101077032A; WO2006071051A1; CA2584334A1; KR101080970B1; CA2584334C

Abstract

A method for controlling an idle mode in a mobile station comprises transmitting an idle mode request to a serving base station to enter the idle mode, and receiving a decode information transmission frame value and a decode information change status from at least one base station. The method also comprises, if the decode information change status indicates a change in the decode information, maintaining the idle mode, and receiving the decode information from the at least one base station when the transmission frame value is reached. The decode information may comprise at least one of downlink channel descriptor (DCD) information, uplink channel descriptor (UCD) information, and forward error correction (FEC) code type information. The transmission frame value may comprise a frame number or a frame offset. The at least one base station may be in a same paging group.

Description

NOTIFICATION OF CHANNEL DESCRIPTOR TRANSMISSION FORA

MOBILE STATION IN IDLE OR SLEEPMODE IN A WIRELESS ACCESS

SYSTEM

TECHNICAL FIELD

The present invention relates generally to a wireless access system and, more

particularly, to idle or sleep mode in a wireless access system.

BACKGROUND ART

A mobile station (MS) operating in sleep or idle mode of a wireless access

system conventionally acts to confirm that sleep or idle mode may be maintained by

continually receiving broadcast messages from a base station (BS), such as a traffic

indicating message and a paging advertising message, and decoding the received

messages to confirm MS status.

Since the traffic indicating message and the paging advertising message include

information related to all nearby mobile stations in sleep or idle mode, the messages

may be very long. Thus, the mobile station may consume much power to decode the

messages.

For most mobile stations, the time required for transmission/reception of data

may be shorter than a standby time for receiving data. Therefore, a mobile station in

sleep mode typically receives a traffic indicating message to continue the sleep mode

(e.g., Negative Indication). Furthermore, a mobile station in idle mode typically

receives a paging advertising message to continue idle mode (e.g., No Action Required).

The sleep mode and idle mode control the mobile station via broadcasting, e.g., the traffic indicating message and the paging advertising message, respectively.

However, when the mobile station in sleep or idle mode unnecessarily decodes

a message, power is unnecessarily consumed by the mobile station.

DISCLOSURE OFTHE INVENTION

Accordingly, the present invention is directed to notification of channel

descriptor transmission for a mobile station in idle or sleep mode that substantially

obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide for transmission of a channel

descriptor in a wireless access system, such that information regarding decode necessity

of a message transmitted in a broadcast format is transmitted to a mobile station. The

channel descriptor information may include a downlink channel descriptor (DCD) or an

uplink channel descriptor (UCD), and/or decode information. The mobile station then

may perform a decode on a necessary message only. Such operation may provide for

reduced power consumption by the mobile station and thereby more efficient

communications .

Additional advantages, objects, and features of the invention will be set forth in

part in the description which follows and in part will become apparent to those having

ordinary skill in the art upon examination of the following or may be learned from

practice of the invention. The objectives and other advantages of the invention may be

realized and attained by the structure particularly pointed out in the written description

and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the

purpose of the invention, as embodied and broadly described herein, in one embodiment, a method for controlling an idle mode in a mobile station comprises transmitting an idle

mode request to a serving base station to enter the idle mode, and receiving a decode

information transmission frame value and a decode information change status from at

least one base station. The method also comprises, if the decode information change

status indicates a change in the decode information, maintaining the idle mode, and

receiving the decode information from the at least one base station when the

transmission frame value is reached.

The decode information may comprise at least one of downlink channel

descriptor (DCD) information and uplink channel descriptor (UCD) information. The

decode information may comprise forward error correction (FEC) code type

information. The transmission frame value may comprise a frame number. The

transmission frame value may comprise a frame offset. The at least one base station

may be in a same paging group. The method may further comprise maintaining the

idle mode if the decode information change status indicates no change in the decode

information.

In another embodiment, a method in a network for controlling an idle mode in a

mobile station comprises receiving an idle mode request from a mobile station to enter

the idle mode, and transmitting a decode information transmission frame value and a

decode information change status to the mobile station. If the decode information

change status indicates a change in the decode information, the mobile station maintains

the idle mode. The method also comprises transmitting the decode information to the

mobile station when the transmission frame value is reached.

The network may comprise at least one base station and a paging controller, the

paging controller configured to control paging within base stations of a paging group. The decode information transmission frame value and the decode information change

status may be broadcast to the mobile station at each paging interval.

The foregoing and other objects, features, aspects and advantages of the present

invention will become more apparent from the following detailed description of the

present invention when taken in conjunction with the accompanying drawings. It is to

be understood that both the foregoing general description and the following detailed

description of the present invention are exemplary and explanatory and are intended to

provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further

understanding of the invention and are incorporated in and constitute a part of this

application, illustrate embodiments of the invention and together with the description

serve to explain the principles of the invention.

FIG. 1 is a block diagram illustrating protocol layers for use in a wireless access

system, according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a subchannel of an OFDMA physical layer,

according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a data region of an OFDMA physical layer,

according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating mapping of an FEC block to an OFDMA

subchannel and an OFDM symbol, according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a frame structure of an OFDMA physical layer

in a wireless access system, according to an embodiment of the present invention. FIG. 6A is a diagram illustrating a MAC PDU format, according to an

embodiment of the present invention.

FIG. 6B is a diagram illustrating a MAC management message format,

according to an embodiment of the present invention.

FIG. 6C is a diagram illustrating a plurality of concatenated MAC PDUs for

transmission as an uplink burst, according to an embodiment of the present invention.

FIG. 7 is a signal flow diagram illustrating idle mode action in a mobile station,

according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a mobile station in idle mode receiving a

DCD/UCD message, according to an embodiment of the present invention.

FIG. 9 is a diagram illustrating a mobile station in idle mode receiving a

DCD/UCD message, according to another embodiment of the present invention.

FIG. 10 is a generalized block diagram of a mobile station, according to an

embodiment of the present invention.

DETAILED DESCRIPTION OFTHE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of the

present invention, examples of which are illustrated in the accompanying drawings.

Wherever possible, the same reference numbers will be used throughout the drawings to

refer to the same or like parts.

The present invention may be embodied in a wireless access system operating

according to the IEEE 802.16e standard. However, the present invention may also be

embodied in wireless access systems operating according to other standards.

The present invention may provide for transmission of a channel descriptor in a wireless access system, such that information regarding decode necessity of a message

transmitted in a broadcast format is transmitted to a mobile station. The channel

descriptor information may include a downlink channel descriptor (DCD) or an uplink

channel descriptor (UCD), and/or decode information. The mobile station then may

perform a decode on a necessary message only. Such operation may provide for reduced

power consumption by the mobile station and thereby more efficient communications.

Actions of a mobile station in sleep mode include repetition of a listening

interval and a sleep interval. The length of the listening interval may be fixed via a sleep

request/sleep response message. During the listening interval, the mobile station may

confirm whether downlink traffic intended for the mobile station and/or whether to

maintain the sleep mode, via a traffic indicating (e.g., MOB_TRF_IND) message

transmitted from a base station. The length of the sleep interval may be determined by a

sleep window. During the sleep interval, the mobile station receives minimal downlink

signals from the base station in order to minimize power consumption.

Actions in sleep mode are performed by sending/receiving management

messages, such as a sleep request (e.g., MOB-SLP-REQ) message, a sleep response

(e.g., MOB-SLP-RSP) message, and/or a traffic indicating message delivered in a

broadcast format between the mobile station and the base station.

Table 1, below, shows an exemplary management message that includes a sleep

interval and a listening interval, delivered for a sleep mode request from a mobile

station to a serving base station.

[Table 1]

Table 2, below, shows an exemplary sleep response (e.g., MOB-SLP-RSP)

message to deliver sleep mode associated information including a presence or non-

presence of sleep mode approval, a sleep interval, a listening interval, and/or a sleep ID

to a mobile station from a serving base station.

[Table 2]

Table 3, below, shows an exemplary broadcast traffic indicating (e.g., TRF-

IND) message delivered at a uniform interval. A mobile station in sleep mode receives a

traffic indicating message during a listening interval to decide whether to maintain the

sleep mode or to receive downlink data by terminating the sleep mode.

[Table 3]

Idle mode supports mobility and increases power efficiency of the mobile

station by receiving a periodic paging advertising (e.g., MOB-PAG-ADV) message at

the mobile station within a paging zone. The paging zone includes a plurality of base

station areas. To configure a paging zone, an inter-base-station message (e.g., Paging- Group-Action) is transmitted between base stations by wire in a format such as that

shown in the below Table 4.

[Table 4]

The inter-base-station message (e.g., Paging-Group-Action) is delivered

between base stations and may be used in various ways according to different

combinations of action bits. In a first usage, a receiving base station (target BS) may be

assigned to a specific paging group (e.g., Action=0). In a second usage, a receiving base

station may be removed from a specific paging group (e.g., Action=l). In a third usage,

a receiving base station may be queried regarding to which group the receiving base

station belongs (e.g., Action=2). In a fourth usage, a receiving base station may be

informed regarding to which paging group a transmitting base station (sender BS)

belongs (e.g., Action=3).

Since a base station may belong to one or more paging zones, the inter-base-

station message may include information related to a plurality of paging groups. Via the

inter-base-station message, base stations may be informed of a paging cycle and a

paging offset used in each paging zone. Furthermore, base stations may be dynamically

assigned to paging groups using the inter-base-station message.

When entering idle mode, a mobile station uses a deregistration request (e.g.,

DREG-REQ) message, such as that shown in the below Table 5.

[Table 5]

Referring to Table 5, a mobile station sets a deregistration request code of the

deregistration request message to 0x01, for example, and then delivers the message to a

base station to request entrance to idle mode. The mobile station may accordingly

deliver a preferred paging cycle. The base station receives the message and may respond

to the request from the mobile station via a deregistration command (e.g., DREG-CMD)

message, such as that shown in the below Table 6.

[Table 6]

Referring to Table 6, the base station may allow the mobile station to enter the

idle mode via Action Code (e.g., Action Code=0x05) of the deregistration command

(e.g., DREG-CMD) message. Alternatively, the mobile station may request to enter the

idle mode after a prescribed duration (e.g., Action Code=0x06). Alternatively, the

mobile station may not request to enter the idle mode until transmitting the

deregistration command message (e.g., Action Code=0x07). Exemplary action codes of

the deregistration command message are shown in the below Table 7.

[Table 7]

0x08-0xFF Reserved

A paging group ID (e.g., Paging Group ID), a paging cycle (e.g., Paging_Cycle)

and a paging offset value (e.g., Paging_Offset), which should be maintained during the

idle mode by the mobile station, may be delivered via a TLV (type length value) item

that may be selectively included in the deregistration message.

The mobile station may then receive a paging advertising (e.g., MOB-PAG-

ADV) message, such as that shown in the below Table 8 during a predefined paging

cycle and paging offset to maintain or terminate the idle mode.

[Table 8]

A wireless access system may define a protocol of a medium access control

(MAC) layer and a physical (PHY) layer for a point-to-multipoint connection between a

base station and a mobile station.

system, according to an embodiment of the present invention.

Referring to FIG. 1, an uppermost part of a MAC layer is a service specific

convergence sublayer, operative to convert various packet data of an upper core network

to a common protocol data unit (PDU) format according to the MAC specification and

to compress a header of the corresponding packet.

A physical layer of the wireless access system may be classified into a single

carrier system and a multi-carrier system (e.g., OFDM/OFDMA). The multi-carrier

system may use orthogonal frequency division multiplexing (OFDM), capable of

allocating resources by subchannel unit grouping. OFDM, in turn, enables orthogonal

frequency division multiple access (OFDMA).

Table 9, below, shows common physical layer characteristics between OFDM

and OFDMA.

[Table 9]

Referring to Table 9, forward error correction (FEC) coding selectively uses a

concatenated code between a Reed-Solomon code (RS code) and a convolutional code

or a block turbo code (BTC) and employs a modulation system of BPSK/QPSK/16-

QAM/64-QAM. FEC coding adopts adaptive modulation/coding (AMC) to select a

modulation mode and a coding rate method according to a channel status. For AMC, a

received signal strength indication (RSSI), a carrier to interface noise ratio (CINR)

and/or a bit error rate (BER) are used in measuring channel quality.

In an OFDMA physical layer, active carriers are separated into groups and are

transmitted per group to a receiving end. The carrier group transmitted to a particular

receiving end is called a subchannel.

FIG. 2 is a diagram illustrating a subchannel of an OFDMA physical layer,

according to an embodiment of the present invention.

Referring to FIG. 2, three exemplary subchannels including subcarriers are

shown. The subcarriers configuring each of the subchannels may lie adjacent to each

other or may be spaced apart from each other at an equal distance. Thus, by enabling

multiple access by subchannel unit, complexity of implementation may increase, but frequency diversity gain, gain according to power concentration, and forward power

control may be efficiently performed. A slot allocated to each user is defined by a data

region of a two-dimensional space. The two-dimensional space is a set of continuous

subchannels allocated by a burst.

FIG. 3 is a diagram illustrating a data region of an OFDMA physical layer,

according to an embodiment of the present invention.

Referring to FIG. 3, a data region of OFDMA may be represented by a rectangle

defined by a time coordinate and a subchannel coordinate.

FIG. 4 is a diagram illustrating mapping of an FEC block to an OFDMA

Referring to FIG. 4, the data region is assigned to an uplink of a specific user.

Alternatively, a base station may transmit the data region to the specific user. To define

such a data region in a two-dimensional space, the number of OFDM symbols in a time

domain and the number of continuous subchannels beginning from a remote location

reference point with an offset in a frequency domain may be provided.

MAC data is segmented according to a FEC block size and each FEC block is

extended to occupy three OFDM symbols on a time axis. Mapping may be sequentially

performed by increasing the subchannel number for each FEC block to arrive at the end

of the data region. Upon reaching the end of the data region, the mapping continues to

be performed from an OFDM symbol with a one-step lower number.

FIG. 5 is a diagram illustrating a frame structure of an OFDMA physical layer

in a wireless access system, according to an embodiment of the present invention.

Referring to FIG. 5, a downlink subframe starts with a preamble used in

synchronization and equalization of a physical layer and then defines a structure of an overall frame via broadcast downlink map (e.g., DL-MAP) and uplink map (e.g., UL-

MAP) messages that define locations and usages of bursts assigned to a downlink and

an uplink, respectively.

Table 10 and Table 11, below, show exemplary of DL-MAP and UL-MAP

messages, respectively.

[Table 10]

[Table 11]

A DL-MAP message defines a usage assigned to each burst for a downlink

section in a burst mode physical layer, and a UL-MAP message defines a usage of a

burst assigned to an uplink section.

Table 12, below, shows an exemplary DL-MAP information element (e.g., DL-

MAP IE).

[Table 12]

In the information elements (IE) for configuring a DL-MAP message shown in

Table 12, a downlink traffic section is divided at a user end by a downlink interval

usage code (e.g., DIUC), a connection ID (e.g., CID), and burst location information

(e.g., subchannel offset, symbol offset, subchannel number, symbol number).

Furthermore, in the information elements for configuring a UL-MAP message

shown in Table 13, a usage is decided for each CID by UIUC and a location of a

corresponding section is specified by a certain duration. In such case, a per-section

usage is determined according to a UIDC value used in the UL-MAP. Each section

begins from a point remote from a previous IE start point according to a duration

specified by the UL-MAP IE.

[Table 13]

A downlink channel descriptor (e.g., DCD) message includes a modulation type

and an FEC code type as physical layer associated parameters to be applied to a burst

section assigned to a downlink. An uplink channel descriptor (e.g., UCD) message

includes a modulation type and an FEC code type as physical layer associated

parameters to be applied to a burst section assigned to an uplink. Moreover, parameters (e.g., 'K', 'R' etc. for R-S code) needed for various forward error correction (FEC) code

types are specified. Such parameters are provided by a burst profile specified per UIUC

(uplink interval usage code) or DIUC (downlink interval usage code) within UCD or

DCD.

Table 14 and Table 15 show examples of DCD and UCD, respectively.

[Table 14]

[Table 15]

- -

Each of the DCD and UCD messages are not transmitted each frame but is

periodically transmitted at a cycle of maximum 10 seconds. Values of Configuration

Change Count included in the DCD and UCD messages are equal to the count values

included in the DL-MAP and UL-MAP shown in the above Table 10 and Table 11,

respectively. Thus, a mobile station may recognize whether the configurations are

changed via the Configuration Change Count values included in the DL-MAP and the

UL-MAP, respectively. If the Configuration Change Count value included in the DL-

MAP or the UL-MAP is changed, the mobile station receives the DCD or UCD message.

A MAC layer of a wireless access system is described below. A CS (service-

specific convergence sublayer) is a layer existing on a MAC CPS (common part sublayer). The CS performs PDU reception from an upper layer, classification of upper

layer PDU, handling of the upper layer PDU based on the classification, delivery of a

CS PDU to an appropriate MAC SAP, and reception of the CS PDU from a peer entity.

The CS is operative in classifying the upper layer PDU per connection, compressing

information of a payload header optionally and/or restoring the compressed header

information.

The MAC CPS maps each packet to a suitable service flow in packet

transmission between a mobile station and a base station on a connection basis and

offers a quality of service (QoS) that varies according to the service flow on the

connection basis. A MAC PDU format defined in the MAC CPS is described below.

FIG. 6A is a diagram illustrating a MAC PDU format, according to an

embodiment of the present invention. FIG. 6B is a diagram illustrating a MAC

management message format, according to an embodiment of the present invention.

Referring to FIGS. 6 A and 6B, MAC PDUs may be classified into a MAC

management PDU and a user data MAC PDU. The MAC management PDU uses a

MAC management message, which is previously specified for an action of a MAC layer,

as a payload. A MAC header is attached to a front end of each payload. A band request

PDU, which is needed to dynamically request a band necessary for each subscriber

adding uplink, corresponds to a specifically formatted MAC management PDU having

only a header called a band request header without a separate payload. A packet PDU

corresponding to user data is mapped to a payload of a MAC SDU. The packet PDU

becomes the MAC PDU by attachment of the MAC header and CRC.

FIG. 6C is a diagram illustrating a plurality of concatenated MAC PDUs for

transmission as an uplink burst, according to an embodiment of the present invention. Referring to FIG. 6C₅ each MAC PDU is identified by a unique connection

identifier (CID). A MAC management message, a band request PDU, and/or user data

(user PDU) may be concatenated to the same burst.

The MAC management message includes a field to indicate a management

message type and a management message payload. Among management messages,

DCD, UCD, UL-MAP, and DL-MAP correspond to the representative management

messages that directly specify the frame structure, the band assignment and the physical

layer parameters.

according to an embodiment of the present invention.

Referring to FIG. 7, a mobile station requests a base station for transition to

sleep mode, maintains the sleep mode, and then terminates the sleep mode when

downlink traffic intended for the mobile station is present, as further described below.

A mobile station sets a sleep request message to values of an initial sleep

interval, a final sleep interval, and a listening interval and then delivers the set message

to a base station to request a transition to sleep mode (S701). In a case where the sleep

mode transition is approved, the base station delivers a sleep response message (S702)

set to the initial sleep interval, the final sleep interval, the listening interval, and a sleep

mode transition start time (start time offset).

When the sleep mode transition start time occurs, the mobile station receives

and decodes all frames during the listening interval. When the initial sleep interval

expires, the mobile station receives a traffic indicating message (S703) from the base

station for the listening interval. If there is no downlink traffic intended for the mobile

station, the mobile station maintains the sleep mode for a period twice the length of the initial sleep interval, for example.

Under the above condition (e.g., a next sleep interval set twice as long as a

previous sleep interval), the sleep interval continues to increase. After the final sleep

interval set by the sleep response message ends, the final sleep interval is repeated as a

next sleep interval. The final sleep interval may be determined by the below Formula 1

via parameters of the sleep response message.

[Formula 1]

final sleep window = final sleep window base * 2 final window exponent

In a case where downlink traffic intended for the mobile station is present, as

indicated via a traffic indicating message, the mobile station terminates the sleep mode

and receives the downlink traffic in normal mode.

Actions of the idle mode are described below.

A paging zone is defined as an overall area covered by base stations included in

a set (e.g., a paging group). The base stations belonging to the same paging group have

the same paging cycle (e.g., Paging_Cycle) and the same paging offset (e.g.,

Paging_Offset).

A mobile station may request a base station for transition to idle mode. The

base station then delivers a paging group ID (e.g., Paging Group ID), a paging cycle

according to the paging group ID, and a paging offset according to the paging group ID

to the mobile station to enable entry to idle mode. During idle mode, the mobile station

may determine whether to maintain idle mode or terminate idle mode via a broadcast

paging advertising message delivered from the base station at each paging cycle.

In a case where uplink traffic is present for the mobile station in idle mode to

transmit, the mobile station may terminate the idle mode. In a case where downlink ~ 2,0 ~

traffic intended for the mobile station in idle mode is present, the base station may

instruct the mobile station to terminate idle mode via the paging advertising message. In

a case where the paging advertising message is not received by the mobile station at a

certain time (for example, if the mobile station in idle mode moves to another paging

zone or loses synchronization to the base station), the mobile station terminates the idle

mode.

To minimize power consumption, a method for early notification of the validity

of the traffic indicating message and paging messages periodically delivered to the

mobile stations in sleep or idle mode, is provided. Accordingly, early notification

information having a suitable length is configured by appropriately grouping the mobile

stations in sleep or idle modes. The early notification information may be delivered to

the mobile stations in sleep or idle mode via a downlink frame.

The early notification information may be delivered in a broadcast via the

downlink frame. If the length of the early notification information is excessive, radio

resources may be wasted. Therefore, configuring early notification information having a

suitable length is provided. To configure early notification information having a suitable

length, a 48-bit MAC address allocated to each mobile station may be used as an

indicator to identify mobile stations in sleep or idle mode, for example.

The number of groups used to classify mobile stations in sleep or idle mode

may be expressed by 'N_Group', for example, hi grouping the mobile stations, the

respective MAC address of the mobile stations may be used for reference, regardless of

whether the mobile stations is in sleep or idle mode. Consequently, a group index (e.g.,

Group_Index) of a group to which a certain mobile station in sleep or idle mode belongs

may be determined using the below Formula 2. [Formula 2]

Grouρ_Index = (MAC address) modulo N_Group

In Formula 2, 'Groupjhidex' means a remainder resulting from dividing a

MAC address of a corresponding mobile station by the number of groups N_Group.

Hence, a value of Group_Index ranges between 0 and (N_Group-l).

For example, in a case where mobile stations in sleep or idle mode are

classified into ten groups (e.g., N_Group=10), a mobile station having a MAC address

of '102' belongs to a 2nd group by '10 modulo (102)'. After completion of the above

grouping procedure, a base station may configure a flag for early notification of mobile

stations belonging to each group. The length of the flag (e.g., a bit number) is equal to

the number of groups. Thus, the length of flag may be determined by 'N_Group'.

If a mobile station that must decode a traffic indicating message or a paging

advertising message is present among a plurality of mobile stations belonging to a

certain group (e.g., if there exists mobile station(s) unable to maintain a sleep or idle

mode), a base station may set a flag for the group to which the corresponding mobile

station belongs to 'positive notification', for example. In such case, the positive

notification may be expressed as ' 1 ' .

If no mobile stations belonging to a certain group need to decode a traffic

indicating message or a paging advertising message, the base station may set a flag for

the corresponding group to 'negative notification', for example. In this case, the

negative notification may be expressed as O'.

In a preferred embodiment of the present invention, it is assumed that five

mobile stations are present having MAC addresses 1, 2, 3, 4 and 5, respectively, and that

the mobile station having the MAC address 3 in the current frame is instructed to decode a traffic indicating message and a paging advertising message. If the five mobile

stations are classified into two groups (i.e., N_Group=2), Group_Index of the mobile

station having the MAC address 2 is set to 0, Group_Index of the mobile station having

the MAC address 4 is set to 0, and each Group_Index of the mobile stations having the

MAC addresses 1 , 3 and 5, respectively, is set to 1 , for example.

To deliver a positive notification to the mobile station having the MAC address

3, a base station sets a flag having a Group_Index of 1 among 2-bit flags to 'positive'.

Therefore, the base station may set flags such as those shown in the below Table 16, for

example.

[Table 16]

The flags may be delivered to the five mobile stations in a broadcast. The

mobile station having a Group_Index with a flag set to 'negative' does not decode the

traffic indicating message or the paging message included in a corresponding downlink

frame.

As explained in the above embodiment, mobile stations may avoid unnecessary

decoding of the traffic indicating message and the paging message via an early

notification flag. Nonetheless, mobile stations belonging to the group set to 'positive'

still decode the traffic indicating message and the paging message.

Furthermore, to increase efficiency via the early notification flag, another

preferred embodiment may be implemented. In the embodiment, a base station is

assumed to know the total number of mobile stations in sleep or idle mode and the

number of mobile stations needing to be set to 'positive' in a current frame. Thus, the - -

base station may determine the number of groups (N_Grouρ) based on the preceding

numbers. By regrouping mobile stations having a Group_Index set to 'positive', the

base station may improve accuracy of the early notification. Accordingly, the mobile

stations having a Group_Index set to 'positive' are classified into N_Positive_Group

groups. An identifier for identifying each of the N_Positive_Group groups may be

defined as a Positive_Group_Index.

In the above embodiment, the mobile stations having Group_Index set to

'positive' are regrouped into N_Positive_Group=3 groups, the mobile station having the

MAC address 1 belongs to the group of which Positive_Group_Index is 1, the mobile

station having the MAC address 3 belongs to the group of which Positive_Group_Index

is 0, and the mobile station having the MAC address 5 belongs to the group of which

Positive_Group__Index is 2, based on Formula 2. Therefore, a final early notification

flag may have a format such as that shown in the below Table 17.

[Table 17]

Consequently, if the base station transmits the early notification flag to the

mobile stations in sleep or idle mode together with values of N_Group and

N_Positive_Group, the mobile stations belonging to the group set to 'positive' decode

the corresponding traffic indicating message and the paging message. However, the

mobile stations belonging to the group set to 'negative' may minimize power

consumption by not decoding the messages. In a case where a mobile station in idle mode needs to receive a DCD/UCD

message, the early notification flag may include information indicating whether the

DCD/UCD message is transmitted in a current frame.

In order for a mobile station in idle mode to enter a network more quickly in

case of uplink/do wnlink traffic occurrence, DCD/UCD variables of a base station within

which the mobile station lies may be stored in the mobile station. Thus, the mobile

station needs to receive the DCD/UCD message whenever the DCD/UCD variables are

changed. The DCD/UCD variables may be changed if the mobile station lies within the

same base station area and/or if the mobile station enters another base station area

belonging to the same paging group.

FIG. 8 is a diagram illustrating a mobile station in idle mode receiving a

DCD/UCD message, according to an embodiment of the present invention.

Referring to FIG. 8, DCD/UCD is transmitted by the same cycle of a variable

called a DCD/UCD transmission cycle (e.g., DCD/UCD Interval). To know whether a

DCD/UCD message is included in a current frame, a mobile station decodes a burst.

Mobile stations in idle mode may determine whether the DCD/UCD is changed using a

DCD count transmitted via a DL-MAP message but may not determine whether the

received message relates to the DCD/UCD until decoding at least part of the burst. Thus,

the mobile station in idle mode should decode all messages broadcast in a downlink

frame until receiving the DCD/UCD message. Thus, significant power consumption

may occur.

FIG. 9 is a diagram illustrating a mobile station in idle mode receiving a

DCD/UCD message, according to another embodiment of the present invention.

Referring to FIG. 9, the base station may transmit information indicating whether a DCD/UCD message is included in a current frame using an early notification

flag. The information indicating whether the DCD/UCD message is included in the

current frame may be transmitted using a DCD/UCD indicator (e.g., DCD/UCD

Indication) of the early notification flag. Therefore, a mobile station may minimize

power consumption by confirming the DCD/UCD Indication of the early notification

flag and then decoding messages broadcast within a downlink frame having the

corresponding value set to 1, for example.

Table 18 shows an exemplary early notification flag.

[Table 18]

- -

The early notification flag may be included as one information element (IE)

included in the DL-MAP message or may be delivered in a separate broadcast message

at the initiation of a downlink frame. Alternatively, the early notification flag may be

delivered over a broadcast channel.

FIG. 10 is a generalized block diagram of a mobile station 1000, according to an

embodiment of the present invention. The methods described herein may be

performed using the mobile station 1000, for example.

Referring to FIG. 10, the mobile station 1000 includes a transmitter 1010 and a

receiver 1060, which operate in conjunction. A processor 1015, which performs

control functions, may be shared by the transmitter 1010 and the receiver 1060.

Alternatively, the transmitter 1010 and the receiver 1060 may have separate processors.

A display 1017, an interface 1019, a speaker 1021, and a microphone 1022 are

operatively coupled to the processor to enable operation of the mobile station 1000 by

the user. A channel coding and a channel decoding 1025 and 1075, respectively, are

operatively coupled to the processor to add redundancy bits, for example, and perform

error correction. A symbol mapping and a symbol demapping 1030 and 1080,

respectively, are operatively coupled to the channel coding and the channel decoding

1025 and 1075, respectively, and serve to map bits to signals, such as QPSK and

16QAM, for example. A subchannel modulation and a subchannel demodulation 1035

and 1085, respectively, are operatively coupled to the symbol mapping and the symbol - -

demapping 1030 and 1080, respectively, and serve to map signals to OFDMA

subcarriers. An IFFT (inverse fast fourier transform) and an FFT (fast fourier

transform) 1040 and 1087, respectively, are operatively coupled to the subchannel

modulation and the subchannel demodulation 1035 and 1085, respectively, and serve to

generate an OFDM wave-formed signal by combining multiple subcarriers. The

mobile station 1000 also includes filters 1045 and 1089, a digital to analog converter

(DAC) 1050, an analog to digital converter (ADC) 1091, and radio frequency

converters (RFs) 1055 and 1093.

In one embodiment, a method for controlling an idle mode in a mobile station

comprises transmitting an idle mode request to a serving base station to enter the idle

mode, and receiving a decode information transmission frame value and a decode

information change status from at least one base station. The method also comprises,

if the decode information change status indicates a change in the decode information,

maintaining the idle mode, and receiving the decode information from the at least one

base station when the transmission frame value is reached.

The decode information may comprise at least one of downlink channel

decode information may comprise forward error correction (FEC) code type

information. The transmission frame value may comprise a frame number. The

may be in a same paging group. The method may further comprise maintaining the

information.

In another embodiment, a method in a network for controlling an idle mode in a - -

mobile station when the transmission frame value is reached.

The network may comprise at least one base station and a paging controller, the

paging controller configured to control paging within base stations of a paging group.

The decode information transmission frame value and the decode information change

status may be broadcast to the mobile station at each paging interval.

Accordingly, the present invention provides early notification of channel

descriptor information from a base station to a mobile station to reduce decoding by the

mobile station. Power consumption may thus be reduced and communications may be

performed more efficiently.

It will be apparent to those skilled in the art that various modifications and

variations may be made in the present invention without departing from the spirit or

scope of the inventions. Thus, it is intended that the present invention covers the

modifications and variations of this invention provided they come within the scope of

the appended claims and their equivalents.

INDERSTRIAL APPLICABILITY

The present invention can be applied to a broadband wireless access system.

Claims

WHAT IS CLAIMED IS

1. A method for controlling an idle mode in a mobile station, the method

comprising:

transmitting an idle mode request to a serving base station to enter the idle mode;

receiving a decode information transmission frame value and a decode information

change status from at least one base station; and

if the decode information change status indicates a change in the decode information:

maintaining the idle mode; and

receiving the decode information from the at least one base station when the

transmission frame value is reached.

2. The method of claim 1, wherein the decode information comprises at

least one of downlink channel descriptor (DCD) information and uplink channel

descriptor (UCD) information.

3. The method of claim 1, wherein the decode information comprises forward

error correction (FEC) code type information.

4. The method of claim 1, wherein the transmission frame value comprises a

frame number.

5. The method of claim 1, wherein the transmission frame value comprises a

frame offset. - —

6. The method of claim 1, wherein the at least one base station is in a same paging

group.

7. The method of claim 1, further comprising:

maintaining the idle mode if the decode information change status indicates no change

in the decode information.

8. A method in a network for controlling an idle mode in a mobile station, the

method comprising:

receiving an idle mode request from a mobile station to enter the idle mode;

transmitting a decode information transmission frame value and a decode information

change status to the mobile station; wherein,

the mobile station maintains the idle mode; and

transmitting the decode information to the mobile station when the transmission frame

value is reached.

9. The method of claim 8, wherein the network comprises at least one base station

and a paging controller, the paging controller configured to control paging within base

stations of a paging group.

10. The method of claim 8, wherein the decode information comprises at least one

of downlink channel descriptor (DCD) information and uplink channel descriptor (UCD) information.

11. The method of claim 8, wherein the decode information comprises forward

error correction (FEC) code type information.

12. The method of claim 8, wherein the decode information transmission frame

value and the decode information change status are broadcast to the mobile station at

each paging interval.

13. A mobile station for controlling an idle mode in a wireless access system, the

mobile station comprising:

means for transmitting an idle mode request to a serving base station to enter the idle

mode;

means for receiving a decode information transmission frame value and a decode

information change status from at least one base station; and

means for maintaining the idle mode; and

means for receiving the decode information from the at least one base station when the

transmission frame value is reached.

14. The mobile station of claim 13, wherein the decode information

comprises at least one of downlink channel descriptor (DCD) information and uplink

channel descriptor (UCD) information.

15. The mobile station of claim 13, wherein the decode information comprises

forward error correction (FEC) code type information.

16. The mobile station of claim 13, wherein the transmission frame value

comprises a frame number.

17. The mobile station of claim 13, wherein the transmission frame value

comprises a frame offset.

18. The mobile station of claim 13, wherein the at least one base station is in a

same paging group.

19. The mobile station of claim 13 , further comprising:

means for maintaining the idle mode if the decode information change status indicates

no change in the decode information.

20. A network for controlling an idle mode in a mobile station, the network

comprising:

means for receiving an idle mode request from a mobile station to enter the idle mode;

means for transmitting a decode information transmission frame value and a decode

information change status to the mobile station; wherein,

the mobile station maintains the idle mode; and

means for transmitting the decode information to the mobile station when the transmission frame value is reached.

21. The network of claim 20, wherein the network comprises at least one base

station and a paging controller, the paging controller configured to control paging within

base stations of a paging group.

22. The network of claim 20, wherein the decode information comprises at least

one of downlink channel descriptor (DCD) information and uplink channel descriptor

(UCD) information.

23. The network of claim 20, wherein the decode information comprises forward

error correction (FEC) code type information.

24. The network of claim 20, wherein the decode information transmission frame

each paging interval.